This invention relates generally to magnetic resonance imaging (MRI), and more particularly the invention relates to steady state free precession (SSFP) imaging in which selective material imaging is achieved using phase detection.
Magnetic resonance imaging (MRI) provides excellent soft tissue contrast with arbitrary scan-volume orientations, thus making MRI an extremely useful medical imaging modality. However, in many applications, MRI is limited by long scan times, limited spatial resolution, and contrast between lipid-based tissue and water-based tissue. Recent advances in gradiant amplifier technology have enabled the use of fully-refocused steady-state free precession (SSFP) imaging methods. SSFP imaging is a very fast method that can provide good tissue contrast and high resolution. A number of commercial implementations of SSFP are available, all of which conceptually identical.
Recently, several methods have been proposed for SSFP imaging with fat suppression, which provides the necessary contrast between water and lipid. Fluctuating-equilibrium MRI, suppression of lipids by RF-modulated FIESTA, and linear-combination SSFP generates steady-state spectral profiles that suppress the frequency band containing lipid tissue. All of these techniques require at least twice the acquisition time of standard SSFP. Magnetization-prepared SSFP methods which manipulate magnetization into the steady-state after a fat-presaturation pulse are only slightly slower than standard SSFP. However, these methods can result in severe artifacts from transient lipid magnetization.